Soil quality is an account of the soil¿s ability to provide ecosystem and social services through its capacities to perform its functions under changing conditions (after Tóth et al. 2007.) The concept of soil quality expressed by this definition allows practical applications with regards to targeted social and/or ecosystem services, including agri-environmental services.
The Thematic Strategy for Soil Protection of the European Union (COM 2006/231) identifies key soil functions of which the maintenance and improvement have to be considered in soil-related policies of the EU. Among the main soil functions several have agri-environmental relevance, which has to be taken into account when developing an Agri-environmental Soil Quality Indicator (AE-SQI).
For agronomic purposes the biomass production function of soil is of absolute importance. This function, however, can be performed under varying external influences. The two main factors conditioning the performance of biomass production of soil are climate and management. During the evaluation of production function, the reacting capacities of soil to these factors need to be considered.
Indication of soil quality from environmental point of view in the agricultural context can relate to off side environmental effects of soil condition and land management practices. The soil¿s capacity to store, filter and transform substances is crucial in this perspective (e.g. carbon storage and climate change; buffering capacity and diffuse contamination). Soil biodiversity can indicate local environmental quality.
Based on the above concept an agri-environmental soil quality indicator is being developed for application in the European Union. The agri-environmental soil quality is expressed by an index constituted by four sub indicators:
¿ Productivity index (the capacity of soil to biomass production)
¿ Fertilizer response rate (input change / yield increase ratio)
¿ Production stability index (the soil-response to climatic variability)
¿ Soil environmental quality index (to express environmental aspects of SQ)
The four sub indicators cover both agronomic and environmental aspects of the goodness of soil (soil quality), therefore constitute to a comprehensive agri-environmental soil quality indicator, which might be applied on different spatial and temporal scales.
The proposed soil quality indicator can be used for policy development (including agricultural and soil protection policies) and monitoring through its capacity:
- to indicate the effect of land use change (marginalization; soil sealing etc.) on the availability and functioning capacity of soil resources;
- to indicate the effect of land management (e.g. intensification) on the functioning capacity of soil resources;
- to indicate the effect of climatic variability on the production function of soil resources;
- to indicate the capacity of soil to mitigate environmental problems (climate change, water pollution etc.).
Based on the information provided by the AE-SQI and its sub-indicators, current levels of soil agri-environmental services can be assessed, monitored and future levels of such services can be projected.